SiC and GaN have attracted attention as semiconductor materials for replacing silicon in semiconductor devices. Both SiC and GaN have bandgaps larger than that of silicon and thus have higher breakdown voltages. Therefore, SiC and GaN can be used to manipulate low on-resistance devices. For this reason, research and development of GaN-based devices is being conducted.
For GaN-based devices, it is difficult to form p-type layers having appropriate characteristics in the GaN material by ion implantation. However, if a high electron mobility transistor (HEMT) structure is used, it is possible to decrease the on-resistance of GaN and use GaN-based components to manipulate devices capable of high-frequency operations.
In designing a high breakdown voltage DC to DC converter using a GaN-HEMT, a diode using a GaN semiconductor material (hereinafter such a diode may be referred to simply as a GaN-Di) is necessary.
However, there is a problem that the leakage current of a GaN-Di during application of a reverse bias can be larger than the leakage current of a GaN-HEMT. Also, a GaN-Di is often formed as a lateral structure, but if a GaN-Di is formed in a lateral structure, the on-resistance generally increases. Therefore, the forward voltage increases and power loss increases.